The present research is directed toward the chemical synthesis of glycosides of biological importance. Diverse protecting groups such as benzyl, allyl, chloroacetyl, and other groups will be utilized in our investigations. Different glycosylating reagents such as oxazolines, 1,2-0-alkyl orthoesters, and 2,3-0-carbonyl-substituted-alpha-D-mannopyranosyl halides containing persistent and temporary protecting groups will be efficiently prepared and further employed in the sequential synthesis of complex saccharides. Halide ion catalyzed reaction will be applied for the preparation of desired 1,2 cis-linked glycosides. The scope of silver triflate as a catalyst in the glycosylation reaction with certain halides will be examined in the studies. We plan to employ an organotin derivative as the key intermediate for selective alkylation of equatorial hydroxy group in vicinal equatorial-axial pair. Generally, the aglycons having persistent protecting groups on other hydroxy groups will be employed as the starting material for the synthesis of higher saccharides. The synthetic saccharides will be useful for the study of glycosidases and glycosyltransferases. In fact, the availability of these synthetic saccharides has led to the discovery of new glycosyltransferases. Our synthetic compounds are being effectively used to determine the specificity of human glycosidases. (A)